One problem related to engine rattling and whining sounds has been reported for the 2013 BMW 335. The most recently reported issues are listed below.
Rattle noise coming from engine compartment or inside of dash upon acceleration (2000-2500rpm) on cold starts. Can change noise based upon acceleration. Goes away after motor warms up (usually 15 minutes) so getting diagnosed at the dealer is difficult. Repeatedly get "can't reproduce problem" back from the dealer. Widespread problem across multiple platforms (2012+ 3 series, 2014+ 4 series).